What is the link between autism and testosterone?

Children who are exposed to high levels of testosterone in the womb show similar results in psychological tests to people with autism. The findings provide support for a contentious theory of the condition's cause, researchers say.

But while the media anticipate autism screening, researchers in the field urge caution, both about the importance of the findings and of the case for screening.

At least four times as many males as females develop autistic disorders. For Asperger's syndrome, the ratio is nine to one1.

Simon Baron-Cohen, a developmental psychologist at the Autism Research Centre at the University of Cambridge, UK, believes that this is because traits associated with autism — such as a difficulty in empathizing and enhanced abilities to analyse, explore and extract the rules that underlie complex systems — are extreme manifestations of normal male behaviour.

Baron-Cohen and his colleagues now report in the British Journal of Psychology that children who had been exposed to high concentrations of testosterone as a fetus are more likely to exhibit autistic traits1. And as high fetal testosterone concentrations have been associated with some aspects of male cognitive ability, they say that their findings provide support for the 'extreme male brain' theory of autism.

But two commentaries23 published in the same issue of the journal show that not everyone agrees about the value of this study, or even on the theory in general.

Testing times

For more than a decade, Baron-Cohen's team has looked at how fetal testosterone concentrations — measured in pregnant women who had the amniotic fluid that surrounded their fetuses tested for medical purposes — correlate with development in 235 children without autism.

The researchers had already found that those children who were exposed to high concentrations of fetal testosterone exhibited some characteristics of adults with autistic disorders, such as making less eye contact, developing fewer interests and having poorer quality relationships1.

Now that the children are on average nine years old, Baron-Cohen and his colleagues have used two questionnaires to look for subtler aspects of autism. The questionnaires asked the mothers about factors such as their children's attention to detail (which is usually high in people with autistic disorders) and ability to know what others are thinking (usually low in people with autism).

Again, they found that the higher the testosterone concentration in the womb, the more similar the results were to those seen in people with autistic disorders.

A special brain?

Psychologist Kate Plaisted Grant, also from the University of Cambridge, calls the study "intriguing", but says that "it doesn't establish a link between fetal testosterone and the cognitive profile of autism". For instance, she says, it does not show a correlation between testosterone and visuospatial skills, in which patients with autism are usually very proficient.

She also isn't convinced that the findings support the underlying theory. "The broader scientific community hasn't accepted the idea of the extreme male brain," she says. Fetal testosterone "may create a special brain, but it doesn't necessarily create a male brain".

Psychiatrist Laurent Mottron, from the University of Montreal in Canada, and an author of one of the commentaries, raises other concerns. In particular, he says that just because males and people with autistic disorders score similarly in autism questionnaires, this does not mean that autistic traits are the same as male traits. Rather, he argues, it just shows that the test cannot discriminate between maleness and autism.

"For me, it's exactly the same as saying that two things that weigh the same are both made of the same stuff," he explains.

Media misinterpretation

Everyone does agree on one thing, however — that the British media has over interpreted the data.

"The Guardian [newspaper] is focusing on the issue of screening. The study is not about screening and it is not motivated by trying to develop the screening test. It was motivated by trying to understand possible causal factors in autism," says Baron-Cohen.

And even if a biological marker for autism is found, many feel that the question of screening is a moral, rather than a scientific, question.

"Individuals with autism are remarkable individuals who have fantastic skills and who are a huge asset to our society," says Plaisted Grant. "The thought that there would be genetic screening so that these individuals wouldn't be born, I find abhorrent."